Globe and globe guard for a lighting fixture

ABSTRACT

A retaining structure for a grid-type globe guard for a lighting fixture, consisting of a internally threaded mounting ring and an externally threaded split guard surrounding a frangible globe, the globe having a beveled flange and the split guard having a chamfered surface which coacts with the bevel to expand the threads into a seizing engagement with the threaded mounting ring as the guard is screwed into place to affix the globe.

United States Patent 1 Bogdanovs I GLOBE AND GLOBE GUARD FOR A LIGHTING FIXTURE [75] Inventor:

[73] Assignee: Grouse-Hinds Company, Syracuse,

[22] Filed: Feb. 5, 1974 [21] Appl. No.: 428,545

Andris Bogdanovs, Liverpool, NY.

[ Sept. 24, 1974 Rl8,l 19 7mm Smith nus 1x14 x FOREIGN PATENTS OR APPLICATIONS 708,443 4/1931 France 240 54 A Primary Exar ninerJoseph F. Peter s, Jr. Attorney, Agent, or Firm-Robert E. Sandt [5 7 ABSTRACT A retaining structure for a grid-type globe guard for a lighting fixture, consisting of a internally threaded mounting ring and an externally threaded split guard surrounding a frangible globe, the globe having a beveled flange and the split guard having a chamfered surface which coacts with the bevel to expand the threads into a seizing engagement with the threaded [56] References Cit d mounting ring as the guard is screwed into place to UNITED STATES PATENTS affix the globe- 890,4l4 6/1908 De Worth 285/243 2 Claims, 3 Drawing Figures I I 3o o Q 1 l 'i-l I H .l 3O I Q I s l.. x I If s vtg a 42 I 43W. I

GLOBE AND GLOBE GUARD FOR A LIGHTING FIXTURE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to lighting fixtures and more particularly to improvements in the structure of a globe and globe guard for securing the globe and guard to the fixture.

2. Description of the Prior Art It has long been a practice in the luminaire art to enclose the lamp in a glass or plastic globe and to protect the globe against physical damage by enclosing it in a metal cage which surrounds the globe. Various methods of securing the globe and guard to the fixture have hitherto been employed. These include threading the globe and guard to separate threaded sections of the fixture, or threading one and bolting the other. However, whenever threaded joints are employed, setscrews or other locking means must be used to prevent loosening under vibration.

SUMMARY OF THE INVENTION It is an object of this invention to provide an improved globe and guard for a lighting fixture, and more particularly to provide means for locking a threaded guard to the fixture without auxiliary means.

It is a further object to provide mating beveled surfaces on the globe and the guard and a split threaded ring on the guard whereby as the guard is threaded into complementary threads on the fixture the coaction of the beveled surfaces cams the split ring and its threads into tight frictional engagement with the threads in the fixture.

The foregoing and other objects, features, and advantages, of the invention will be apparent from the following more particular description of the preferred embodiment of the invention, as illustrated in the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FlG. 1. Is an overall isometric view showing the mounting ring, guard, and globe in position for assembly.

FIG. 2. Is a partial sectional view of the mounting ring, guard, and globe.

FIG. 3. Is an enlarged sectional view of the globe and guard showing the beveled flange and coacting chamfer.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings the cup 40 is bolted, or otherwise fastened to a lighting fixture (not shown). A reflective liner or gasket 43 is provided against which the transparent globe seals. A central aperture in the cup allows the fixture lamp to project into the globe.

Internal threads 42 coact with complementary threads 32 on a one piece globe guard 30 preferably cast in metal. This guard has a split threaded ring, split into two parts by slots 36 (only one of which shows), diametrically opposed. The split ring is joined by means of the vertical and arcular ribs into a unitary yieldable structure having a slight elasticity.

A beveled inner lower surface 34 on the globe guard 30 coacts with a complementary bevel 24 on globe guard 20. When the guard is placed around the globe 20 and first threaded into the cup the beveled surface 34 is above the first beveled surface 22 of the globe. As the globe 20 bottoms against gasket 43 in cup 40 and the guard 30 is tightened, the guard 30 slips downwardlyand outwardly over the bevel 22 to engage the threads 32 and 42. Continued tightening causes the coacting surfaces 24 and 34 to spread the split ring, widening the slots 36, to cam the split ring radially outward to cramp the mating threads and lock the guard to the cup. The locking action is enhanced by the fact that both the cup 40 and guard 30 are cast, thus producing roughened threads to increase the locking friction.

Because of the interference of the threads, and their rough surface, no further locking means are required. Additionally the construction provides the alternative of converting existing fixtures with no guard to one with a guard by substituting a slightly smaller diameter globe and the locking guard structure. Globe guards are now required by many safety standards, where they were formerly not required.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

l. A self-locking globe and globe guard assembly for a lighting fixture comprising:

a. an internally threaded cuplike structure integral with the fixture,

b. an open'ended globe having a generally cylindrical shape and having an external circumferential beveled surface adjacent its open end with the bevel extending outwardly toward the open end of the globe, and

c. a cagelike globe guard having ribs joining a split ring structure in a unitary assembly, the said ring having external threads complementary to the internal threads on said cup, the said ring having an internal beveled surface complementary to the beveled surface on said globe when said guard is assembled over said globe,

. whereby when said guard is assembled around said globe and threaded into said cup the coacting beveled surfaces on the globe and the guard coact to cam said split ring radially outward to produce a tight coaction of the mating threads to provide a tight friction lock between the threads to prevent rotation of the guard in the cup.

2. The assembly of claim 1 wherein the guard and the cup are provided with cast threads to increase the friction between the mating threads. 

1. A self-locking globe and globe guard assembly for a lighting fixture comprising: a. an internally threaded cuplike structure integral with the fixture, b. an open-ended globe having a generally cylindrical shape and having an external circumferential beveled surface adjacent its open end with the bevel extending outwardly toward the open end of the globe, and c. a cagelike globe guard having ribs joining a split ring structure in a unitary assembly, the said ring having external threads complementary to the internal threads on said cup, the said ring having an internal beveled surface complementary to the beveled surface on said globe when said guard is assembled over said globe, d. whereby when said guard is assembled around said globe and threaded into said cup the coacting beveled surfaces on the globe and the guard coact to cam said split ring radially outward to produce a tight coaction of the mating threads to provide a tight friction lock between the threads to prevent rotation of the guard in the cup.
 2. The assembly of claim 1 wherein the guard and the cup are provided with cast threads to increase the friction between the mating threads. 